Studies on decays of light mesons 9th Workshop on Hadron Physics in - - PowerPoint PPT Presentation

Studies on decays of light mesons

9th Workshop on Hadron Physics in China and Opportunities Worldwide Lena Heijkenskjöld Institut für Kernphysik, JGU Mainz 24-29 July 2017

Experiments Dalitz plot studies Transition Form Factors

Introduction

• L. Heijkenskjöld

KPH, JGU Mainz 24-29 July 2017 1/13

Light meson decays Three different but complementary experiments WASA-at-COSY KLOE/KLOE-2 A2 Focus on: Dalitz plot studies Transition form factor measurements

Experiments Dalitz plot studies Transition Form Factors

WASA-at-COSY

• L. Heijkenskjöld

KPH, JGU Mainz 24-29 July 2017 2/13

Wide Angle Shower Apparatus Operated at Cooler Synchrotron (COSY) 2006-2015. COSY — (un)polarised proton/deutron beam p = 600 - 3700 MeV/c. Frozen pellet target — hydrogen/deuterium. Designed for studies of light mesons. p + p → p + p + X

• r

p + d → 3❍❡ + X

H.-H. Adam et al arXiv:nucl-ex/0411038

EDDA

PAX WASA ANK E

Elec t ron c

• oler

St

• c

hast icc

• oling

J ESSICA

Quadrupole Dipole RF c avit y Barrier buc k et c avit y Ex t rac t ion

TOF JULIC

Central Detector ∼ 4π coverage of decay particles Mini drift chamber: 17 cylindrical layers Calorimeter: 1012 CsI(Na) crystals Solenoid: Bmax =1.3T Forward Detector Clean tagging of recoil particles Plastic scintillators Proportional chamber

Experiments Dalitz plot studies Transition Form Factors

KLOE/KLOE-2

• L. Heijkenskjöld

KPH, JGU Mainz 24-29 July 2017 3/13

K LOng Experiment At DAΦNe — e+e− collider √s = MΦ = 1019.4 MeV. e+ + e− → Φ → X + Y + ... KLOE operated 2000-2006. collecting 2.5fb−1 @ MΦ + 250 pb−1 off-peak → Upgraded to KLOE-2, will collect >5 fb−1 2014-2018

• F. Bossi, et al. , Nuovo Cimento, 30 (2008) 10
• G. Amelino-Camelia et al., Eur. Phys. J. C, 68 (2010) 619

Drift Chamber 4m diameter, 3.3 m long ∂p⊥/p⊥ < 0.4% (θ > 45◦) σxy = 150µm, σz =2mm Calorimeter Pb/scintillating fiber 98% coverage of solid angle σT = 57 ps /

• E(GeV) ⊕ 140 ps

Magnetic field B=0.52 T Figure from E. Perez del Rio presentation at International Workshop

• n e+e− collisions from Phi to Psi 2017

For θγ down to 10◦ Quadropole coverage for KL decays Improved vertex reconstruction and track parameters e+e− taggers for γγ physics

Experiments Dalitz plot studies Transition Form Factors

A2

• L. Heijkenskjöld

KPH, JGU Mainz 24-29 July 2017 4/13

A2 At MAinzer MIkrotron (MAMI) — (un)polarised electron accelerator, Emax = 1.6 GeV. Electrons + radiator → tagged bremsstrahlung photons (un/linearly/circularly polarised) γ + p → p + X

• A. Starostin, et al., Phys. Rev. C 64, 055205 (2001)
• R. Novotny, IEEE Trans. Nucl. Sci. 38, 379 (1991)
• J. C. McGeorge Eur. Phys. J. A (2008) 37: 129-137

The Glasgow photon tagger + The end point tagger The Crystal Ball + TAPS setup

C

• llim

a tor Ta rge t Foca l Pla ne Ra dia tor MAMI Be a m Prim a ry Be a m e

• Ele

ctron La dde r E γ= E 0– E e

• Ma

gne t S pe ctrom e te r

Dump Glasgow T agger Photon Beam Photon Beam Radiator Detector

(47 Channels)

Correction Magnet End Point T agger Electron Beam Resolution:

Eγ = 80 - 1401 MeV Resolution: 1-4 MeV

Bremsstrahlung Probability [a.u] Meson Photoproduction Cross Section T agger EPT

1 10 10² 10³ 0.5 1 1.5 σ [µbarn]

total π⁰ η' η ω

/ [GeV] E 1 2 3 4 5 6 7 8 9

Crystal Ball TAPS Target, PID & MWPC Vetos

672 NaI(TI) crystals 366 BaF , 72 PbWO crystals

2 4

384 plastic scintillators

Photon beam

Experiments Dalitz plot studies Transition Form Factors

What is a Dalitz plot?

• L. Heijkenskjöld

KPH, JGU Mainz 24-29 July 2017 5/13

Kinematic variables 3-body decay: A given by two independent variables → 2D representation.

]

2

[GeV

12

s

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5

]

2

[GeV

23

s

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5

sij =|Pi +Pj |2

Common choice of variables when m1 = m2

X

• 1
• 0.5

0.5 1

Y

• 1
• 0.5

0.5 1

X= √ 3

T∗ 1 −T∗ 2 Q

Y=

(2m1+m3)T∗ 3 (m1Q)

−1

Z

0.2 0.4 0.6 0.8 1

Φ

• 3
• 2
• 1

1 2 3

Z=X2+Y 2 Φ= tan−1 X

Y

Parametrisation To compare experimental/theory results — only for smooth distributions. |A(X, Y)|2 ∝ N(1 + aY + bY 2 + cX + dX 2 + eXY + fY 3 + gX 2Y + ...) |A(Z, Φ)|2 ∝ N(1 + 2αZ + 2βZ 3/2 sin(3Φ) + 2γZ 2 + 2δZ 5/2 sin(3Φ) + ...)

Experiments Dalitz plot studies Transition Form Factors

η → π+π−π0

• L. Heijkenskjöld

KPH, JGU Mainz 24-29 July 2017 6/13

Study ratio of light mq AχPT

LO

∼ Q−2 =

m2

d −m2 u

m2

s−m2 ud

0.2 0.4 0.6 0.8 1 5 10 15 20 25

mu md ms md

QD We inbe rg 77

• L. Caldeira Balkeståhl, Doctoral

dissertation Uppsala U. 2016

NNLO χPT calculated1 — slow convergence Dispersive calculations2,3 — use χPT constraints and exp. results → Q

1 J. Bijnens, et al., JHEP 11 (2007) 030, 2 G. Colangelo, et al.,Phys.Rev.Lett. 118, (2017) 022001, 3 P . Guo, et al., arXiv:1608.01447 [hep-ph]

− − − − − − − − − −

Experiments Dalitz plot studies Transition Form Factors

η → π+π−π0

• L. Heijkenskjöld

KPH, JGU Mainz 24-29 July 2017 6/13

Study ratio of light mq AχPT

LO

∼ Q−2 =

m2

d −m2 u

m2

s−m2 ud

0.2 0.4 0.6 0.8 1 5 10 15 20 25

mu md ms md

QD We inbe rg 77

• L. Caldeira Balkeståhl, Doctoral

dissertation Uppsala U. 2016

NNLO χPT calculated1 — slow convergence Dispersive calculations2,3 — use χPT constraints and exp. results → Q

1 J. Bijnens, et al., JHEP 11 (2007) 030, 2 G. Colangelo, et al.,Phys.Rev.Lett. 118, (2017) 022001, 3 P . Guo, et al., arXiv:1608.01447 [hep-ph]

Experimental Dalitz plots KLOE e+e− → φ → γη WASA pd → 3Heη High statistics Dalitz plot density distribution. Fit parametrisation → test of theory. Determination of theory parameters → Q

KLOE

X 1 − 0.8 − 0.6 − 0.4 − 0.2 − 0.2 0.4 0.6 0.8 1 Y 1 − 0.8 − 0.6 − 0.4 − 0.2 − 0.2 0.4 0.6 0.8 1

5000 10000 15000 20000 25000

• A. Anastasi, et al., JHEP 1605 (2016) 019

WASA

X

• 1
• 0.5

0.5 1

Y

• 1
• 0.5

0.5 1

0.01 0.02 0.03 0.04 0.05 0.06 0.07

P . Adlarson, et al., Phys.Rev. C90 (2014) no.4, 045207

Experiments Dalitz plot studies Transition Form Factors

ω → π+π−π0

• L. Heijkenskjöld

KPH, JGU Mainz 24-29 July 2017 7/13

Study decay dynamic

Z

00.1 0.20.30.40.50.60.70.80.9 1

Φ

• 3
• 2
• 1

1 2 3 0.02 0.04 0.06 0.08 0.1

• 6

10 ×

ω π ρ π π Final state P-wave π − π interactions — Previously unmeasured Full predictions by lagrangian approaches4 and dispersion calculations5,6.

4 [Uppsala]C. Terschlüsen, et al., Eur.Phys.J. A49 (2013) 116 5 [Bonn] S.P . Schneider, et al., Eur.Phys.J. C72 (2014) 2012 6 [JPAC] I. Danilkin et al., Phys. Rev. D91 (2015) 094029

❍❡

Experiments Dalitz plot studies Transition Form Factors

ω → π+π−π0

• L. Heijkenskjöld

KPH, JGU Mainz 24-29 July 2017 7/13

Study decay dynamic

Z

00.1 0.20.30.40.50.60.70.80.9 1

Φ

• 3
• 2
• 1

1 2 3 0.02 0.04 0.06 0.08 0.1

• 6

10 ×

ω π ρ π π Final state P-wave π − π interactions — Previously unmeasured Full predictions by lagrangian approaches4 and dispersion calculations5,6.

4 [Uppsala]C. Terschlüsen, et al., Eur.Phys.J. A49 (2013) 116 5 [Bonn] S.P . Schneider, et al., Eur.Phys.J. C72 (2014) 2012 6 [JPAC] I. Danilkin et al., Phys. Rev. D91 (2015) 094029

Experimental Dalitz plot WASA pd → 3❍❡ω and pp → ppω (4.408 ± 0.042) × 104 events A ∼ [Pwave] ×

• 1 + 2αZ + 2βZ 3/2 sin 3φ + O(Z 2)
• −

→ First observation of intermediate ρ ∝ α parameter

P . Adlarson, et al., Phys.Lett. B770 (2017) 418

Experiments Dalitz plot studies Transition Form Factors

η′ → ηπ0π0

• L. Heijkenskjöld

KPH, JGU Mainz 24-29 July 2017 8/13

η′ → ηππ: Test for Resonance ChPT7,9, large-NC ChPT8,9 and Dispersive approach10

7

• G. Ecker, et al., Phys. Lett. B 223 (1989) 425, 8
• R. Kaiser et al., Eur. Phys. J. C 17 (2000) 623, 9

Escribano, et al. JHEP 1105 (2011) 094, 10

• T. Isken et al.,

arXiv:1705.04339

Cusp effect η’ η π+ π− π0 π0

11Kubis, et al., Eur.Phys.J. C62 (2009) 511-523

Not yet observed in this channel NREFT11 → (a2 − a0): ππ S-wave scat. lengths for I=0,2

Experiments Dalitz plot studies Transition Form Factors

η′ → ηπ0π0

• L. Heijkenskjöld

KPH, JGU Mainz 24-29 July 2017 8/13

η′ → ηππ: Test for Resonance ChPT7,9, large-NC ChPT8,9 and Dispersive approach10

7

• G. Ecker, et al., Phys. Lett. B 223 (1989) 425, 8
• R. Kaiser et al., Eur. Phys. J. C 17 (2000) 623, 9

Escribano, et al. JHEP 1105 (2011) 094, 10

• T. Isken et al.,

arXiv:1705.04339

Cusp effect η’ η π+ π− π0 π0

11Kubis, et al., Eur.Phys.J. C62 (2009) 511-523

Not yet observed in this channel NREFT11 → (a2 − a0): ππ S-wave scat. lengths for I=0,2 Experimental Dalitz plot

P . Adlarson, presentation at International Workshop

• n e+e− collisions from Phi to Psi 2017

A2 γp → η′p 120 000 events in Dalitz plot − → Fit 1 + aY + bY 2 + cX + dX 2 − → Fit cusp to get (a2 − a0)

Experiments Dalitz plot studies Transition Form Factors

Transition Form Factors

• L. Heijkenskjöld

KPH, JGU Mainz 24-29 July 2017 9/13

Input to aSM

µ

3-4σ discrepancy in aSM

µ

− aexp

µ

— Data driven efforts to reduce theoretical error 12,13.

12 G. Colangelo, et al. Phys.Lett. B738 (2014) 6-12 13 V. Pauk, et al., Phys.Rev. D90 (2014) no.11, 113012

Theory contribution aµ × 1011 QED14 115965218.178(0.077) EW15 153.6(1.0) Strong16 HVP 6793.6(41.4) HLbL 103(29)

14 Aoyama, et al., Phys.Rev.Lett. 109 (2012) 111808 15 Gnendiger, et al, Phys.Rev. D88 (2013) 053005 16 Jegerlehner, arXiv:1705.00263 [hep-ph]

Hadronic light-by-light scattering: γ γ∗ γ∗ γ∗ µ µ ≈ γ γ∗ γ∗ γ∗ µ µ P∗

P∗ = π∗, η∗, η′∗

+ . . . → F(P∗ → γ(∗)γ(∗)) Measurable form factors Space-like e+ e− γ∗ γ∗ P Time-like e+ e− γ∗ γ P P γ γ∗ e+ e−

Experiments Dalitz plot studies Transition Form Factors

Transition Form Factors

• L. Heijkenskjöld

KPH, JGU Mainz 24-29 July 2017 9/13

Input to aSM

µ

3-4σ discrepancy in aSM

µ

− aexp

µ

— Data driven efforts to reduce theoretical error 12,13.

12 G. Colangelo, et al. Phys.Lett. B738 (2014) 6-12 13 V. Pauk, et al., Phys.Rev. D90 (2014) no.11, 113012

Theory contribution aµ × 1011 QED14 115965218.178(0.077) EW15 153.6(1.0) Strong16 HVP 6793.6(41.4) HLbL 103(29)

14 Aoyama, et al., Phys.Rev.Lett. 109 (2012) 111808 15 Gnendiger, et al, Phys.Rev. D88 (2013) 053005 16 Jegerlehner, arXiv:1705.00263 [hep-ph]

Hadronic light-by-light scattering: γ γ∗ γ∗ γ∗ µ µ ≈ γ γ∗ γ∗ γ∗ µ µ P∗

P∗ = π∗, η∗, η′∗

+ . . . → F(P∗ → γ(∗)γ(∗)) Measurable form factors Space-like e+ e− γ∗ γ∗ P Time-like e+ e− γ∗ γ P P γ γ∗ e+ e−

Experiments Dalitz plot studies Transition Form Factors

Transition Form Factors

• L. Heijkenskjöld

KPH, JGU Mainz 24-29 July 2017 10/13

Dalitz decays P γ γ∗ e+ e− P V V γ γ∗ e+ e− Study of P → γl+l− V → Pl+l− Extracting the form factor Normalised FF — FP(q2, 0) = FP(q2, 0) FP(0, 0) dΓ(P → γe+e−) dq2Γ(P → γγ) = [QED]P

• FP(q2, 0)
• 2

Compare results — VMD-inspired parametrisation F(q2, 0) ≈ 1 + Λ−2q2

Experiments Dalitz plot studies Transition Form Factors

P → γe+e−

• L. Heijkenskjöld

KPH, JGU Mainz 24-29 July 2017 11/13

π0 → γe+e−

A217 γp → π0p 4 · 105 events aπ = 0.030(10)

• aπ

m2

π0

= Λ−2

• ∼ factor 2 better precision from NA62.

→ Future plans from A2 to match.

17 P . Adlarson, et al., Phys.Rev. C95 (2017) no.2, 025202 ]

2

[GeV/c

• e

+

e

m

0.02 0.04 0.06 0.08 0.1 0.12 0.9 0.95 1 1.05 1.1 1.15 1.2 1.25 1.3

p0 0.009552 ± 0.02983 p0 0.009552 ± 0.02983 p0 0.009552 ± 0.02983 p0 0.009552 ± 0.02983

(c)

This Work: Data This Work: Fit approxim. e Pad DA

Experiments Dalitz plot studies Transition Form Factors

P → γe+e−

• L. Heijkenskjöld

KPH, JGU Mainz 24-29 July 2017 11/13

π0 → γe+e−

A217 γp → π0p 4 · 105 events aπ = 0.030(10)

• aπ

m2

π0

= Λ−2

• ∼ factor 2 better precision from NA62.

→ Future plans from A2 to match.

17 P . Adlarson, et al., Phys.Rev. C95 (2017) no.2, 025202 ]

2

[GeV/c

• e

+

e

m

0.02 0.04 0.06 0.08 0.1 0.12 0.9 0.95 1 1.05 1.1 1.15 1.2 1.25 1.3

p0 0.009552 ± 0.02983 p0 0.009552 ± 0.02983 p0 0.009552 ± 0.02983 p0 0.009552 ± 0.02983

(c)

This Work: Data This Work: Fit approxim. e Pad DA

]

2

) [GeV/c

• l

+

l m(

0.1 0.2 0.3 0.4 0.5 2

|

η

|F

1 p0 0.008521 ± 1.004 p1 0.1301 ± 1.969 p0 0.008521 ± 1.004 p1 0.1301 ± 1.969 p0 0.008521 ± 1.004 p1 0.1301 ± 1.969 p0 0.008521 ± 1.004 p1 0.1301 ± 1.969

(a)

This Work: Data This Work: Fit A2, 2014 A2, 2011 TL calculation

• appr. (2014)

e Pad

]

2

) [GeV/c

• l

+

l m(

0.1 0.2 0.3 0.4 0.5 1

(b)

This Work: Data This Work: Fit NA60, In-In NA60, p-A DA (with a2)

• appr. (2015)

e Pad

η → γe+e−

A218 γp → ηp 5.4 · 104 events Good experiment - theory agreement. Ongoing study with WASA19 pp → ppη

18 P . Adlarson, et al., Phys.Rev. C95 (2017) no.3 035208 19 A. Goswami, JPS Conf.Proc. 13 (2017) 020032

Experiments Dalitz plot studies Transition Form Factors

P → γe+e−

• L. Heijkenskjöld

KPH, JGU Mainz 24-29 July 2017 11/13

π0 → γe+e−

A217 γp → π0p 4 · 105 events aπ = 0.030(10)

• aπ

m2

π0

= Λ−2

• ∼ factor 2 better precision from NA62.

→ Future plans from A2 to match.

17 P . Adlarson, et al., Phys.Rev. C95 (2017) no.2, 025202 ]

2

[GeV/c

• e

+

e

m

0.02 0.04 0.06 0.08 0.1 0.12 0.9 0.95 1 1.05 1.1 1.15 1.2 1.25 1.3

p0 0.009552 ± 0.02983 p0 0.009552 ± 0.02983 p0 0.009552 ± 0.02983 p0 0.009552 ± 0.02983

(c)

This Work: Data This Work: Fit approxim. e Pad DA

]

2

) [GeV/c

• l

+

l m(

0.1 0.2 0.3 0.4 0.5 2

|

η

|F

1 p0 0.008521 ± 1.004 p1 0.1301 ± 1.969 p0 0.008521 ± 1.004 p1 0.1301 ± 1.969 p0 0.008521 ± 1.004 p1 0.1301 ± 1.969 p0 0.008521 ± 1.004 p1 0.1301 ± 1.969

(a)

This Work: Data This Work: Fit A2, 2014 A2, 2011 TL calculation

• appr. (2014)

e Pad

]

2

) [GeV/c

• l

+

l m(

0.1 0.2 0.3 0.4 0.5 1

(b)

This Work: Data This Work: Fit NA60, In-In NA60, p-A DA (with a2)

• appr. (2015)

e Pad

η → γe+e−

A218 γp → ηp 5.4 · 104 events Good experiment - theory agreement. Ongoing study with WASA19 pp → ppη

18 P . Adlarson, et al., Phys.Rev. C95 (2017) no.3 035208 19 A. Goswami, JPS Conf.Proc. 13 (2017) 020032

η′ → γe+e−

Ongoing study with A220 γp → η′p mee up to 840 MeV — cover ρ peak

20 O. Steffen, EPJ Web Conf. 142 (2017) 01027

Experiments Dalitz plot studies Transition Form Factors

V → Pe+e−

• L. Heijkenskjöld

KPH, JGU Mainz 24-29 July 2017 12/13

ω → π0e+e−

Significant disagreement between theory – experiment (NA60, Lepton-G) A221 γp → ωp 1100 events Λ−2

ωπ0 = 1.99(22tot) GeV−2

21 P . Adlarson et al., Phys.Rev. C95 (2017) no.3, 035208

]

2

) [GeV/c

• l

+

l m(

0.1 0.2 0.3 0.4 0.5 0.6

2

|

π ω

|F

1 10

2

10

p0 0.05529 ± 1.006 p1 0.2206 ± 1.989 p0 0.05529 ± 1.006 p1 0.2206 ± 1.989 p0 0.05529 ± 1.006 p1 0.2206 ± 1.989 p0 0.05529 ± 1.006 p1 0.2206 ± 1.989

(a)

This Work: Data This Work: Fit NA60, In-In VMD TL calculation Caprini, N/D Canterbury appr.

]

2

) [GeV/c

• l

+

l m(

0.1 0.2 0.3 0.4 0.5 0.6 1 10

2

10

(b)

This Work: Data This Work: Fit NA60, p-A Lepton-G ] π 3 → ω DA [full Caprini, DA

Experiments Dalitz plot studies Transition Form Factors

V → Pe+e−

• L. Heijkenskjöld

KPH, JGU Mainz 24-29 July 2017 12/13

ω → π0e+e−

Significant disagreement between theory – experiment (NA60, Lepton-G) A221 γp → ωp 1100 events Λ−2

ωπ0 = 1.99(22tot) GeV−2

21 P . Adlarson et al., Phys.Rev. C95 (2017) no.3, 035208

]

2

) [GeV/c

• l

+

l m(

0.1 0.2 0.3 0.4 0.5 0.6

2

|

π ω

|F

1 10

2

10

p0 0.05529 ± 1.006 p1 0.2206 ± 1.989 p0 0.05529 ± 1.006 p1 0.2206 ± 1.989 p0 0.05529 ± 1.006 p1 0.2206 ± 1.989 p0 0.05529 ± 1.006 p1 0.2206 ± 1.989

(a)

This Work: Data This Work: Fit NA60, In-In VMD TL calculation Caprini, N/D Canterbury appr.

]

2

) [GeV/c

• l

+

l m(

0.1 0.2 0.3 0.4 0.5 0.6 1 10

2

10

(b)

This Work: Data This Work: Fit NA60, p-A Lepton-G ] π 3 → ω DA [full Caprini, DA

VMD DA UChT

φ → π0e+e−

KLOE22 e+e− → φ 9500 events (First!) Cover higher mee region — closer look at discrepancy. Λ−2

Φπ0 = 2.02(11) GeV−2

22 A. Anastasi et al., Phys.Lett. B757 (2016) 362-367

Experiments Dalitz plot studies Transition Form Factors

V → Pe+e−

• L. Heijkenskjöld

KPH, JGU Mainz 24-29 July 2017 12/13

ω → π0e+e−

Significant disagreement between theory – experiment (NA60, Lepton-G) A221 γp → ωp 1100 events Λ−2

ωπ0 = 1.99(22tot) GeV−2

21 P . Adlarson et al., Phys.Rev. C95 (2017) no.3, 035208

]

2

) [GeV/c

• l

+

l m(

0.1 0.2 0.3 0.4 0.5 0.6

2

|

π ω

|F

1 10

2

10

p0 0.05529 ± 1.006 p1 0.2206 ± 1.989 p0 0.05529 ± 1.006 p1 0.2206 ± 1.989 p0 0.05529 ± 1.006 p1 0.2206 ± 1.989 p0 0.05529 ± 1.006 p1 0.2206 ± 1.989

(a)

This Work: Data This Work: Fit NA60, In-In VMD TL calculation Caprini, N/D Canterbury appr.

]

2

) [GeV/c

• l

+

l m(

0.1 0.2 0.3 0.4 0.5 0.6 1 10

2

10

(b)

This Work: Data This Work: Fit NA60, p-A Lepton-G ] π 3 → ω DA [full Caprini, DA

VMD DA UChT

φ → π0e+e−

KLOE22 e+e− → φ 9500 events (First!) Cover higher mee region — closer look at discrepancy. Λ−2

Φπ0 = 2.02(11) GeV−2

22 A. Anastasi et al., Phys.Lett. B757 (2016) 362-367

φ → ηe+e−

KLOE23 e+e− → φ ∼ 3 · 104 events Better correspondence to VMD. Λ−2

Φη = 1.17(10)(+7) (−11) GeV−2

23 D. Babusci et al., Phys.Lett. B742 (2015) 1-6

Experiments Dalitz plot studies Transition Form Factors

Summary

• L. Heijkenskjöld

KPH, JGU Mainz 24-29 July 2017 13/13

Studies of light meson decays WASA-at-COSY — pp / pd KLOE — e+e− A2 — pγ Dalitz plot studies η → 3π — Light quark mass ratio ω → 3π — ππ dynamics η′ → ηππ — ππ S-wave scattering lenghts Transition form factors P → γe+e− — Good theory accord V → Pe+e− — Theory disagreement

Experiments Dalitz plot studies Transition Form Factors

Summary

• L. Heijkenskjöld

KPH, JGU Mainz 24-29 July 2017 13/13

Studies of light meson decays WASA-at-COSY — pp / pd KLOE — e+e− A2 — pγ Dalitz plot studies η → 3π — Light quark mass ratio ω → 3π — ππ dynamics η′ → ηππ — ππ S-wave scattering lenghts Transition form factors P → γe+e− — Good theory accord V → Pe+e− — Theory disagreement

Thank you for your attention!

Experiments Dalitz plot studies Transition Form Factors

Backup — η → π+π−π0

• L. Heijkenskjöld

KPH, JGU Mainz 24-29 July 2017 13/13

TABLE I: Summary of Dalitz plot parameters from experiments and theoretical predictions.

E xp erim ent −a b d f −g Gormley(70) [16] 1.17 ± 0.02 0.21 ± 0.03 0.06 ± 0.04 − − Layter(73) [17] 1.080 ± 0.014 0.03 ± 0.03 0.05 ± 0.03 − − CBarrel(98) [18] 1.22 ± 0.07 0.22 ± 0.11 0.06(f i xed) − − KLOE(08) [19] 1.090 ± 0.005+0.019

−0.008

0.124 ± 0.006 ± 0.010 0.057 ± 0.006+ 0.007

−0.016

0.14 ± 0.01 ± 0.02 − WASA(14) [20] 1.144 ± 0.018 0.219 ± 0.019 ± 0.047 0.086 ± 0.018 ± 0.015 0.115 ± 0.037 − BESIII(15) [21] 1.128 ± 0.015 ± 0.008 0.153 ± 0.017 ± 0.004 0.085 ± 0.016 ± 0.009 0.173 ± 0.028 ± 0.021 − C alcu lat ion s ChPT LO [10] 1.039 0.27 − ChPT NLO [10] 1.371 0.452 0.053 0.027 − ChPT NNLO[10] 1.271 ± 0.075 0.394 ± 0.102 0.055 ± 0.057 0.025 ± 0.160 − dispersive [22] 1.16 0.26 0.10 − − simplif ed disp [5] 1.21 0.33 0.04 − − NREFT [12] 1.213 ± 0.014 0.308 ± 0.023 0.050 ± 0.003 0.083 ± 0.019 0.039 ± 0.002 UChPT [11] 1.054 ± 0.025 0.185 ± 0.015 0.079 ± 0.026 0.064 ± 0.012 −

KLOE(16) 1.095(3)+(3)

−(2)

0.145(3)(5) 0.081(3)+(6)

−(5)

0.141(7)+(7)

−(8)

0.044(9)+(12)

−(13)

xFit

• A. Anastasi, et al., JHEP 1605 (2016) 019

Experiments Dalitz plot studies Transition Form Factors

Backup — ω → π+π−π0

• L. Heijkenskjöld

KPH, JGU Mainz 24-29 July 2017 13/13

• I. Danilkin, et al., Phys.Rev. D91 (2015) no.9, 094029

WASA(17) α = 147(36) × 103

P . Adlarson, et al., Phys.Lett. B770 (2017) 418-425

Experiments Dalitz plot studies Transition Form Factors

Backup — V → γe+e−

• L. Heijkenskjöld

KPH, JGU Mainz 24-29 July 2017 13/13

π0 → γe+e−

NA62 aπ = 0.0368(57)

• aπ

m2

π0

= Λ−2

• C. Lazzeroni, et al., Phys.Lett. B768 (2017) 38-45

η′ → γe+e−

Ongoing study with A2 A2 - simulation

]

2

[GeV

2

q 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 ' events η # 1 10

2

10

Simulation VMD fit QED calculation Simulation VMD fit QED calculation

• O. Steffen, EPJ Web Conf. 142 (2017) 01027

BESIII — Λ−2 = 1.60 ± 0.17stat ± 0.08sys GeV−2

Λ−2

VMD = 1.45 GeV−2 and Λ−2 χPT = 1.60 GeV−2

)

2

) (GeV/c

• e

+

M(e

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

2

)|

2

|F(q

1 10

• M. Ablikim et al., Phys.Rev. D92 (2015) no.1, 012001